#define _CRT_SECURE_NO_WARNINGS

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode* left, TreeNode* right) : val(x), left(left), right(right) {}
    
};
class Solution {
public:
    string tree2str(TreeNode* root) {
        if (root == nullptr)
        {
            return string("");
        }

        string ret;
        ret += to_string(root->val);

        if (root->left != nullptr || (root->left == nullptr && root->right != nullptr))
        {
            ret += "(";
            ret += tree2str(root->left);
            ret += ")";
        }


        if (root->right != nullptr)
        {
            ret += "(";
            ret += tree2str(root->right);
            ret += ")";
        }
        return ret;
    }
};